Target masking


Furuno Fan

I am trying to select the ideal way to reflect bottom structure detail to feed Maxsea's PBG and one area that is somewhat confusing is target masking. As mentioned previously, target area is between 200 and 400 meters and I am searching for drop off's. With an R309 transducer with a DFF3 at 200 meters the high frequency will cover between 17 and 22 meters while the low will cover between 50 and 60 meters. My questions are:

1. What will be displayed as depth (NMEA DPT) if I am only using the low frequency and the drop off area is directly below the boat with the area covered by the cone angle having depths between 200 and 230 meters?
2. What bottom structure will be displayed if both high and low frequencies are being displayed?

I have seen some of the pictures you have posted on bottom, mostly using both frequencies, and it seems they are always showing the bottom as having the same depth so I am confused. Today I use a B265 where the low frequency cone angle is 23º so the real drop off could be as far as 33 meters off the side of the boat!

Your best vertical definition will be from the narrowest beam possible. The wider the beam, the less defined any bumps or holes will be.